The theft of wireless telecommunications service is a major problem for a wireless service provider. Traditionally, a thief steals wireless service by "cloning" a legitimate user's wireless terminal and by using the clone to a place call, which is then billed to the legitimate user. Typically, a thief clones a wireless terminal by using a sophisticated radio to eavesdrop on a legitimate wireless call and to obtain the legitimate user's wireless terminal's authentication codes. When the thief has obtained the authentication codes, the thief re-programs another wireless terminal with the authentication codes, which results in a clone.
To combat the ease with which authentication codes can be stolen through eavesdropping, authentication codes are now typically encrypted when they are transmitted to and from the wireless terminal. Although this precaution usually precludes the theft of wireless service through eavesdropping, it does not, however, eliminate all theft of wireless service.
Because a wireless terminal is small and portable, a thief can easily steal a legitimate wireless terminal and use the wireless terminal to steal wireless service. To prevent a thief from using a stolen wireless terminal to steal wireless service, a wireless telecommunications system can incorporate a password-based system that must be satisfied before an outgoing call can be initiated or an incoming call can be answered.
In accordance with the password-based system, the wireless service provider and each authorized user agree on a personal identification number ("PIN"), which is stored in the wireless telecommunications system's subscriber database as part of the user's record. Thereafter, when the user initiates a call from the wireless terminal, the wireless telecommunications system makes an authentication request. The authentication request prompts the user to enter a candidate PIN into his or her wireless terminal and to transmit the candidate PIN to the wireless telecommunications system. If, and only if, the candidate PIN matches the PIN in the database does the wireless telecommunications system complete the call. Presumably, the thief of a wireless terminal would not know the user's PIN and would, therefore, be thwarted from using the wireless terminal to place a call.
Although this technique is effective, it has three main disadvantages. First, the technique often works only for calls initiated within the authorized user's home wireless service area. Therefore, a thief can still succeed in stealing wireless service by taking the wireless terminal out of the authorized user's home wireless service area, or, alternatively, by stealing a wireless terminal from a user who is traveling outside the user's home area. Second, most users are annoyed at having to enter their PIN each time they initiate a call. And third, the transmission of the authentication request, the transmission of the PIN and the subsequent delay while the PIN is being confirmed by the wireless service provider all consume air time, which is inevitably paid for by the user, and delays the user in reaching their desired party.
Alternatively, a wireless telecommunications system could reduce the annoyance to a user by requiring the PIN to be transmitted only after power-up but before the first call is placed. However, this technique compromises security for safety, since the wireless terminal can be stolen before it is powered off.
Some wireless terminals have a provision that prevents a call from being initiated unless the user enters a key sequence that matches a PIN stored in the terminal before each call is initiated. This technique is, advantageous because it works outside of the wireless terminal's home area and because there is no air time consumption. The technique is annoying, however, because a user must still enter a candidate PIN before each call is initiated.
Therefore, the need exists for a more advantageous technique that prevents the thief of a wireless terminal from stealing wireless service.